慢性肾病中FGF23致冠状动脉微循环障碍机制的心肌声学造影无创活体研究

One of the major refractory complications of chronic kidney disease is heart failure, which is currently believed to be caused by coronary microvascular dysfunction. Many clinical studies have shown that the occurrence of cardiovascular disease in patients with chronic nephropathy is closely associated with high circulating levels of fibroblast growth factor 23 (FGF23). Recent studies have indicated that elevated FGF23 can cause vascular endothelial injury. Therefore, excessive FGF23 levels may result in coronary microvascular dysfunction by impairing vascular endothelial function, which ultimately leads to heart failure in patients with chronic kidney disease; inhibition of FGF23 can be an effective treatment to improve coronary microcirculation. However, this hypothesis lacks in vivo experimental evidence. The proposed project intends to adopt Myocardial Contrast Echocardiography technology to accurately quantify blood flow in coronary microcirculation by measuring the uptake rate of microbubbles with strong scattering characteristics. The technique has its intrinsic features of non-invasive, visual and precise; and can be applied, in a real-time, dynamic and in vivo manner, to determine the extent of coronary microvascular dysfunction caused by FGF23, as well as to evaluate the therapeutic effects of FGF23 inhibition in coronary microcirculation improvement. The proposed project will therefore not only innovatively evaluate coronary microvascular dysfunction using microbubble echocardiography, but also provide experimental evidence for clinical evaluation of coronary microvascular dysfunction in patients with chronic nephropathy and additionally, for treatment and follow-up studies.

慢性肾病的严重难治性并发症之一是心力衰竭，目前认为其主要病理基础是冠状动脉微循环障碍。多项临床研究表明，慢性肾病患者心脏疾病的发生与血液中高浓度成纤维细胞生长因子23（FGF23）密切相关。新近研究提示FGF23增高可造成血管内皮损伤。因此，慢性肾病患者体内高浓度FGF23可能通过损伤微循环内皮功能造成冠脉微循环障碍，进而导致心衰发生；抑制FGF23有可能成为改善冠脉微循环的有效治疗方法。但该假设尚缺乏有效活体实验证据。本项目拟通过采用心肌声学造影技术，利用微泡的强散射性特征，测量其浓聚速率，准确定量冠脉微循环血流量。该技术具有无创、直观、精确的特点，可实时、动态、活体观察FGF23变化致冠脉微循环障碍的程度，评估抑制FGF23对改善冠脉微循环的治疗作用。本研究创新性的采用微泡造影评价慢性肾病并发冠脉微循环障碍，并为临床工作中评价慢性肾病患者冠脉微循环障碍及治疗随访提供重要实验依据。

心血管病变是慢性肾病的严重并发症，严重肾功能减低患者的心衰发病率是正常肾功能人群的两倍以上，严重影响慢性肾病患者的预后。越来越多的研究显示，此类患者的冠状动脉微循环存在病变，可能是导致患者最终心衰的重要因素。慢性肾病患者由于钙磷代谢紊乱导致FGF23明显升高，FGF23被证实可引起主动脉内皮功能减低，导致血管扩张受限，血流量减低，冠状动脉微循环血流对心肌功能的影响至关重要，但这一假说在冠状动脉微循环水平未得到充分证实，此外也尚无微循环影像学手段进行活体研究来评价FGF23对微循环作用。本研究的主要内容是通过应用心肌声学造影技术，评价慢性肾病5/6肾切除模型大鼠的冠状动脉微循环血流量，以乙酰胆碱为负荷药物，诱导内皮细胞释放NO，观察对照组和慢性肾病组在乙酰胆碱诱导下冠状动脉充盈速度，定量评价心肌血流，比较两组大鼠血流增加倍数是否存在差异，并在分子生物水平对两组进行比较，验证NO释放量的差异。通过研究发现，模型组大鼠的肌酐水平、FGF23水平明显高于对照组，在乙酰胆碱作用下模型组的冠状动脉灌注水平的增长低于对照组大鼠。分离的大鼠冠状动脉微循环动脉在FGF23孵育后对乙酰胆碱反应性明显减低，NO释放水平减低。我们的研究为慢性肾病通过FGF23导致微循环功能障碍提供了实验依据，同时证明了通过超声微泡造影剂计算心肌血流灌注可以在活体水平评价微循环功能障碍，为临床应用该技术评价慢性肾病患者的微循环功能提供了依据。